I wonder how the "choose your own api key" policy is going to work in practice... given that people don't usually make very secure passwords and that the example is "Real estate website" you're going to get some pretty easy to guess api keys.
That's actually just a name to identify the API key, the actual API key is a 40-character automatically generated string. The idea is that you will be able to create an API key for each of your projects and revoke them individually as necessary.